/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.obfuscate;

import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.util.SimplifiedVisitor;

/**
 * This AttributeVisitor trims and marks all local variable (type) table attributes that it visits. It keeps parameter
 * names and types and removes the ordinary local variable names and types.
 *
 * @author Eric Lafortune
 */
public class ParameterNameMarker extends SimplifiedVisitor implements AttributeVisitor {
    private final AttributeVisitor attributeUsageMarker;

    /**
     * Constructs a new ParameterNameMarker.
     * 
     * @param attributeUsageMarker the marker that will be used to mark attributes containing local variable info.
     */
    public ParameterNameMarker(AttributeVisitor attributeUsageMarker) {
        this.attributeUsageMarker = attributeUsageMarker;
    }

    // Implementations for AttributeVisitor.

    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}

    public void visitLocalVariableTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute,
        LocalVariableTableAttribute localVariableTableAttribute) {
        if (!AttributeUsageMarker.isUsed(localVariableTableAttribute) && hasParameters(clazz, method)) {
            // Shift the entries that start at offset 0 to the front.
            int newIndex = 0;

            for (int index = 0; index < localVariableTableAttribute.u2localVariableTableLength; index++) {
                LocalVariableInfo localVariableInfo = localVariableTableAttribute.localVariableTable[index];

                if (localVariableInfo.u2startPC == 0) {
                    localVariableTableAttribute.localVariableTable[newIndex++] = localVariableInfo;
                }
            }

            // Trim the table.
            localVariableTableAttribute.u2localVariableTableLength = newIndex;

            // Mark the table if there are any entries.
            if (newIndex > 0) {
                attributeUsageMarker.visitLocalVariableTableAttribute(clazz, method, codeAttribute,
                    localVariableTableAttribute);
            }
        }
    }

    public void visitLocalVariableTypeTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute,
        LocalVariableTypeTableAttribute localVariableTypeTableAttribute) {
        if (!AttributeUsageMarker.isUsed(localVariableTypeTableAttribute) && hasParameters(clazz, method)) {
            // Shift the entries that start at offset 0 to the front.
            int newIndex = 0;

            for (int index = 0; index < localVariableTypeTableAttribute.u2localVariableTypeTableLength; index++) {
                LocalVariableTypeInfo localVariableTypeInfo =
                    localVariableTypeTableAttribute.localVariableTypeTable[index];

                if (localVariableTypeInfo.u2startPC == 0) {
                    localVariableTypeTableAttribute.localVariableTypeTable[newIndex++] = localVariableTypeInfo;
                }
            }

            // Trim the table.
            localVariableTypeTableAttribute.u2localVariableTypeTableLength = newIndex;

            // Mark the table if there are any entries.
            if (newIndex > 0) {
                attributeUsageMarker.visitLocalVariableTypeTableAttribute(clazz, method, codeAttribute,
                    localVariableTypeTableAttribute);
            }
        }
    }

    // Small utility methods.

    private boolean hasParameters(Clazz clazz, Method method) {
        return method.getDescriptor(clazz).charAt(1) != ClassConstants.METHOD_ARGUMENTS_CLOSE;
    }
}